Solvatochromatic properties

Huddleston, J. G., Broker, G. A., Willauer, H. D., Rogers, R. D., Free-energy relationships and solvatochromatic properties of l-alkyl-3-methylimidazolium ionic liquids. In Ionic Liquids, ACS Symposium Series 818, 270-288, 2002. 

EXPERIMENT 9.2 INVESTIGATING SOLVATOCHROMATIC PROPERTIES OF VANADYL-d/s(2,4-PENTANEDIONE), VO(acac)2 USING VISIBLE SPECTROSCOPY... 

For the analysis of SN1 solvolyses, Abraham et al. (9) have proposed an equation (equation 3) based on sensitivities toward solvatochromatic properties. In equation 3, tr is a measure of solvent dipolarity-polarization, a is a measure of solvent hydrogen bond donor acidity, and P is a measure of solvent hydrogen bond acceptor basicity. More recently, a term governing cavity effects has been added, and this term is considered to represent an important contribution (10, 11). The cavity term can be directly related to the square of the Hildebrand solubility parameter (10-12). A similar analysis by Koppel and Palm (13, 14) involves terms governed by solvent polarity, solvent polarizability, electrophilic solvation ability, and nucleophilic solvation ability. Recently, a cavity term has also been added to this analysis (12). 

Altered physical-chemical and solvatochromatic properties (e.g., solubility, volatility, critical micelle concentration [CMC])... 

While it appears that a good deal of the QEO susceptibility may be accounted for by three terms, yc, yn, and yrp, we do not intend to ignore the potential importance of other terms in Equation (9). The strategy will be to see where a reasonable cut-off of terms of Equation (9) can still lead to an adequate explanation of the structure/property trend. We are presently working on solvatochromatic and EFISH determinations of A ioi, with the aim to more fully characterize molecules with regard to yn, and have plans to experimentally determine in order to calculate yrp- There are also efforts underway to more accurately determine orientational contributions. 

Carceroisomerism has also been observed in hemicarceplexes. Paek and coworkers have measured isomerisation energy barriers of carceroisomers in non-centrosymmetric C4v hemicarceplexes, the largest of which was found to be 15.4 Kcal mol-1 for the rotation of NMP inside the cavity [43]. It has also been claimed that the inside of carcerands and hemicarcerands can be considered as a new phase of matter. This suggestion implies effects beyond mere spatial confinement and chemical isolation, for example, a marked change in the physical bulk properties, such as the polarity or polarisability of the host cavity. Nau has obtained evidence that biacetyl included within the cavity of a hemicarcerand may experience an unusual polarisability even higher than that of di-iodomethane by using biacetyl as a solvatochromatic probe for the polarisability of the environment [44]. 

In our study, the properties of the microenvironment of synthetic polymers were investigated by means of various solvatochromic reporters l-methacryloyloxyethyl-4-carboalkoxypyridinium salts (SCHEME I), 1-alkyl-4-/4-hydroxystyryl/pyridinium-betaine (SCHEME II) and spiropyran-merocyanine type (SCHEME ID) all have solvatochromatic bands in the visible absorption l-dimethylaminonaphthalene-5-sulphonamido chro-mophore (SCHEME IV) has a solvatochromic band in the emission spectrum. 

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